The present invention relates to SELF CONTAINED PRESSURE SENSITIVE THERMAL TRANSFER LABELS & MEDIA making. Self contained thermal transfer media can also be used as tags, tickets, receipts, fax and other digitally imaged thermally on demand.
Thermal printing has made possible cost effective digital imaging under computer control. Thermal printing makes possible one of the most accurate methods of printing machine readable bar codes. Dots printed can be overlapped producing very distinct edges needed in bar codes.
Thermal printing can be segregated into two principal categories.
Direct thermal printing functions to print an image directly on paper stock caged with heat sensitive chemicals. Because of the simplicity of the technology and cost effective in manufacturing, the population of the direct thermal printers in use today is numbered over three million world wide. Direct thermal images lack dimensional stability and resistance to physical and chemical reaction. The image thus made have problems in image stability, which gave rise to the introduction of thermal transfer printers. However, because of the higher costs of manufacturing, the population of direct thermal printers is greater than that of the thermal transfer printers. This invention is intended to allow direct thermal printers to produce images comparable to those produced by the more expensive thermal transfer printers.
Thermal printing techniques can generally be segregated into two principal categories: direct thermal printing and thermal transfer printing. Direct thermal printing functions to print an image directly on the paper stock, coated with heat sensitive material. In thermal transfer printing, a thermal transfer ribbon is applied upon the paper stock before the paper stock is passed through the thermal printer. The thermal transfer ribbon, or donor ribbon generally appears similar to carbon paper, with a wax or wax-resin coating formed on the undersurface. As the paper stock/donor ribbon is passed through the thermal printer, the print head functions to melt the wax onto the underlying paper stock in prescribed patterns. The donor ribbon is then removed from the paper stock, leaving the image formed by the thermal print head.
Thermal transfer printing has advantages that make this technology attractive. In thermal transfer printing, the ink is directly applied to the paper stock, whereas with the direct thermal transfer, no ink is used. Instead, the image arises from reaction of the heat sensitive coating as the paper stock passes adjacent the thermal print head. As a result, thermal transfer printing typically can result in a higher quality printing that resists fading and allows for long-term storage and scanability. Thermal transfer printing also lends itself to color printing, allows high graphics contrast capability and provides substantial flexibility in the papers stock or other receiving media to be printed on.
Despite the foregoing advantages, there are also disadvantages associated with thermal transfer printing. Many of those disadvantages arise from the requirement that the donor ribbon, be reliably applied in flat registry with the paper stock, then removable from the paper stock after printing. Typically, the thermal transfer ribbon is wound on a separate dispensing spool and mated to the paper stock as it reaches the thermal print head. Thereafter, the used ribbon is separated from the paper stock and rewound onto a retrieval roller. Such procedures require mechanisms that are incompatible with the large population of compact thermal printers that are currently used for many applications. Moreover, difficulties may arise in winding and rewinding the donor ribbon, wrinkling of the ribbon as it is applied to the paper, and recyclability of the donor ribbon after it is used. Disposability of the donor ribbon can be a significant problem, because many such ribbons do not readily degrade. Special treatments needed to dispose of the donor ribbon, adding cost to the labels.
In some cases, the donor ribbon is not rewound after passing through the thermal print head, but rather remains on the paper stock, and separated in use. While such techniques avoid the need for retrieving the donor ribbon, they give rise to additional difficulties resulting from adhering the donor ribbon to the paper stock. In particular, as the donor ribbon is removed from the paper stock, adhesive may remain on the paper stock causing the paper stock to be gummy, interfering with the scanability of the printed image and interfering in the ability of the paper stock to pass through dispensing mechanisms and other devices.
Accordingly, there is a need for apparatus and techniques to allow for the thermal transfer printing of labels which allows the label to be printed on conventional direct thermal printers, without the need for retrieval rollers to collect the used thermal transfer ribbon. Additionally, it is desirable that the resulting labels be cuttable to size as desired, with little or no adhesive remaining on the label after the thermal transfer ribbon is removed.
Another aspect of the present invention concerns the ability to generate secure facsimile based communications. In some cases it is desirable that communications received by facsimile are not disclosed to personnel other than the intended recipient. Use of the present invention provides for a product and technique whereby, except for the transmission cover page, only the intended recipient will review the communication. By means of the present invention, it would be readily detectible if anyone would remove donor ribbon, which is necessary to read the communication.
Accordingly, the present invention not only allows existing direct thermal printers to print higher quality documents, but also allows the documents to be communicated in a secure mode.
These and other advantages and features are achieved in the present invention as described below.